One of the most important applications of methods for determining the phase angle difference between two alternating electrical signals is the measurement of fluid flow by using a flowmeter that generates two alternating electrical signals with a phase angle difference therebetween varying as a function of the flow rate of fluids. For example, the mass flow rate of media moving through a flexurally vibrating conduit is proportional to the phase angle difference between two alternating electrical signals respectively representing the flexural vibrations of the two opposite halves of the vibrating conduit included in a convective inertia force flowmeter (Coriolis force flowmeter). Earlier inventions made by one or more of the inventors of the present invention disclose methods for determining flow rate of fluids moving through a rotameter as a function of the phase angle difference between two alternating electrical signals representing the position of the float included in the rotameter, and methods for determining the level of liquids as a function of the phase angle difference between two alternating electrical signals representing the position of a float floating on the free surface of liquids (U.S. patent application Ser. No. 036,953); and methods for determining the position and velocity of an object as a function of the phase angle difference between the transmitted wave towards the object and the reflected wave from the object and as a function of the time rate of change of the phase angle difference, respectively (U.S. patent application Ser. No. 024,222). In addition to the afore-mentioned applications, there are numerous other applications of the methods for determining the phase angle difference between two alternating electrical signals in the engineering, industrial and scientific fields as well as in the commercial and military areas. Therefore, a highly economic and extremely accurate method for determining the phase angle difference between two alternating electrical signals has an important ramification in terms of technical applications as well as financial value.